Speed controlled fuel system



y 1952 E. o. WlRTH ETAL SPEED CONTROLLED FUEL SYSTEM Filed May 29, 1947 p E 5 0 F M M g M MWK f M W W Patented May 27, 1952 SPEED CONTROLLED FUEL SYSTEM Emil 0. Wirth and Frederik Barfod, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application May 29, 1947, Serial No. 751,288

9 Claims.

The present invention relates to fuel supply systems for internal combustion engines, burners and the like and more particularly to an improved fuel system in which liquid fuel is supplied under superatmospheric pressure to an enine or the like.

One of the primary objects of the present invention is to provide a fuel metering system for an engine adapted to operate under extreme conditions.

Another object of the invention is to provide a fuel metering system for an engine wherein the fuel is metered by varying the fuel pressure both upstream and downstream from a variable size metering orifice.

Another object is to provide, in a pressure fuel metering system having a fuel discharge valve, an idle cut-off mechanism to prevent the discharge of fuel while the engine is inoperative irrespective of the absolute fuel pressure of the system.

Another object of the invention is to provide a fuel system for an engine wherein the fuel is under superatmospheric pressure from the source to the induction passage and in which the fuel pressure may vary appreciably without having any substantial effect on the metering characteristics of the system.

Still another object is to provide a closed fuel system for an engine wherein the fuel vapors forming in the system may be removed before they adversely affect the fuel metering characteristics of the system.

A further object of the invention is to provide a mechanism, including an idle cut-off in a pressure responsive fuel discharge valve, for balancing the fiuid pressure in said valve when the engine becomes inoperative.

Further objects and advantages will be apparent from the following description and accompanying drawings wherein one specific embodiment of our improved fuel metering system is given. In the drawings, the present fuel metering system is shown schematically and includes generally a tank It] as a source of fuel, a fuel injector device I2 from which the fuel is delivered to an engine (not shown) and a conventional fuel pump l4 adapted to receive fuel from said tank and to deliver it to said device at a substantially constant pressure.

Referring first to the fuel injector device I2, numeral 20 designates an induction passage, 22 a throttle valve, 24 an intake manifold, and 26 a fuel discharge nozzle, said nozzle preferably, but not necessarily, being located on the engine side of the throttle valve. An air cleaner or the like .may be included in the induction system, preferably secured to the fuel injector device at the intake side of the induction passage adjacent shoulder 21. The general arrangement of several of the basic elements comprising the present device is shown and claimed in our copending application Serial No. 674,868, filed June 6, 1946 and now Patent Number 2,452,627, issued November 2. 1948.

The fuel enters the injector from conduit 28 and passes through passage 30 into the fuel inlet of a centrifugal pump 32 consisting of an impeller 34 mounted on a shaft 36 adapted to be driven by the engine (not shown) at a speed directly proportional to the speed of said engine to build up an outlet pressure for the metering head in the fuel system. The impeller is provided with a plurality of radially extending blades which receive fuel from the inlet adjacent the impeller shaft 36 and discharge it into an annular channel 38 and thence into conduit 40 which communicates through metering orifice 42 and conduit 44 with chamber 46. Chamber 46 communicates with induction passage 20 through discharge nozzle 26 which, for the purpose of illustration, is shown as a plain tube with the discharge end thereof beveled in the direction of the air flow through the induction passage. During. the operation of the engine, the pressure in conduit 40 anterior to the metering orifice is at all times greater than the impeller inlet pressure by an amount directly proportional to the square of the impeller speed and therefore is proportional to the square of the engine speed. The pressure in conduit 44 and chamber 46 during operation is always less than the pressure in conduit 40 anterior to the metering orifice 42, the difference in the two pressures being the effective metering head across said metering orifice.

A mechanism, shown generally at numeral 48,

for varying the effective size of metering orifice 42 is preferably included in order to obtain special metering characteristics for certain operating conditions, such as a rich mixture for starting and a lean mixture for economical engine operation. A suitable valve construction for varying the size of said metering orifice is described and claimed in our copending application Serial No. 747,113, filed May 9, 1947.

A fuel control chamber 50 is disposed adjacent chamber 46 and is separated therefrom by a fluid impervious flexible diaphragm 54, the margin of said diaphragm being clamped in place in a fluid tight relationship between the body of the injector and a spacer ring 58. The central portion of diaphragm 54 is a thickened section having a flat smooth side adjacent the discharge nozzle and is adapted to fluctuate toward and away from the end of said nozzle in response to the variations in the pressure on either side thereof to variably regulate the effective size of the inlet to said nozzle and thereby to regulate the discharge of fuel in accordance with the requirements of the engine. Any other suitable valve construction which is capable of varying the size of an orifice in accordance with the differential between two fluid pressures may be substituted for the one shown schematically in the drawings.

Chamber 50 is connected by a conduit 62 with passage 30 anterior to impeller 34, conduit 62 being provided with an accurately made orifice 64 opening directly into chamber 50. Chamber 50 is connected to conduit 40 on the posterior side of said impeller by conduit 66, orifice 68, chamber 70 and conduit 12. The pressure of the fuel in conduit 66 and chamber 50 is controlled by varying the effective area of orifice 68 which permits the high pressure fuel from the outlet of the impeller to enter conduit 66 and chamber 50. The means for varying the effective size of orifice 68 comprises a tapered valve 14 connected to or formed integrally with a fluted valve stem 16 and adapted to move'longitudinally in said orifice. Stem 16, which is slidably received in guide 18, is secured at its outer end 82 to a flexible diaphragm as by the deformation of said end around apertures in said diaphragm and stiifening members 84 and 86. The stiffening members, which are provided to render the central portion of the diaphragm 8B inflexible, consist of metal plates having their edges rolled outwardly to prevent the diaphragm from being punctured or otherwise injured by sharp edges or burrs on the plate. In the assembled fuel system, diaphragm 80 is secured in place by the marginal area thereof being clamped between casing 88 and the body portion of injector l2. The chamber 10 is connected directly with the impeller outlet pressure in conduit 40 by conduit 12 and is therefore subjected to the unmetered fuel pressure which constantly urges diaphragm 89 in the direction to open valve With the fuel flowing through orifice 68, passage 66, chamber 50 and orifice 64, a pressure is created in chamber 50 of a value intermediate the unmetered fuel pressure in conduit 40 and the impeller inlet pressurein passage 30, the value of this intermediate pressure depending upon the relative sizes of orifices 64 and 68. Consequently, if orifice 68 has an effective area equal to that of orifice 64, the pressure in chamber 50 will remain substantially half-way between the pressure of the unmetered fuel in conduit 40 and the pressure of the fuel in conduit 30 anterior to the impeller irrespective of variations in impeller speed.

The position of valve 14 in orifice 68 is controlled in accordance with the position of throttle valve 22 through cam 90 mounted on a throttle valve shaft 92 and rigidly secured thereto by nut 94, said throttle valve being actuated by an accelerating lever or any equivalent thereof or controlled by a governor through any well-known connecting means mounted on the free end of shaft 92. The contour of cam 90 is such that the effective area of orifice 68 is decreased by the opening movement of throttle valve 22. It is seen that when the throttle valve is moved in the opening direction, the effective size of orifice 68 is restricted to an effective area less than that at closed throttle by tapered valve 14 so that the pressure in chamber 50 more nearly approaches the impeller inlet pressure. As a result of this unbalanced condition between chambers 46 and 59, diaphragm 54 moves toward chamber 50 and thus away from the inlet of discharge nozzle 26, permitting a greater discharge of fuel into the induction passage. When the throttle valve is moved in the closing direction, the effec-' tive area of orifice 6B is increased, causing the pressure of the fuel in chamber 50 temporarily to exceed that of the fuel in chamber 46. The diaphragm consequently moves toward the nozzle inlet, restricting the discharge of fuel from chamber 46 so that the pressure in said latter chamber increases until it becomes equal to the pressure in chamber 50. Further, in the event the pressure of the metered fuel in chamber 46 should tend to exceed the pressure of that behind the diaphragm 54, as a result of increased fuel delivery by the impeller, the diaphragm will move away from the nozzle inlet, permitting the excess fuel to discharge into the induction passage at an increased rate such that the pressures on either side of the diaphragm will again become substantially equalized.

A mechanism for automatically shutting off the flow of fuel from the discharge nozzle when the engine stops is provided and includes a relatively weak coil spring 96 in a chamber 98 reacting between the head of spring guide I00 and the inner surface of casing I02. Said guide is slidably received in a centrally located bore in boss I 04 and the head thereof abuts against the con tral portion of diaphragm I05 and under the force of spring urges said diaphragm toward diaphragm 54. Chamber 98, which is separated from chamber 50 by the fuel impervious diaphragm I05, is connected by conduits I06 and I08 with fuel tank 10 so that pressure in said chamher will be maintained the same as that in tank i0. Conduit I05 is connected by a passage III) with passage 30 anterior to the centrifugal pump, and chamber 50 is connected with passage 30 by conduit 62. Chamber 4B communicates with passage 30 through conduits 40 and 44 and impeller 34, whether the impeller is rotating or not. With this arrangement the pressures in chambers 46, 50 and 98 readily become equalized when the engine becomes inoperative, permitting diaphragms 54 and H15 to float between the chambers. Thus spring 96, which is made relatively weak so that it will not interfere with proper operation of the fuel discharge jet, can readily move diaphragm I05 against diaphragm 54 and force the central portion 60 of the latter diaphragm against the inner end of discharge nozzle 26 to prevent the discharge of fuel until the engine, on becoming operative, increases the pressure of the fuel in chambers 46 and 50 over that in chamber 98. By the use of the second diaphragm 105, spring 96 does not affect the operation of diaphragm 54 while the engine is in operation.

In order to prevent the vapor in the fuel from affecting the metering characteristics of the fuel metering device, passage Ill] connecting passage 30 anterior to the centrifugal pump with conduit H16 permits the vapors to separate from the fuel before the fuel enters the impeller. The vapors return to the fuel tank through conduit M8.

The present fuel metering system is adapted to operate in any off-vertical position and is a closed system wherein fuel is delivered from the tank to the discharge nozzle under superatmospheric pressure. In the operation of the-engine, tank 10 is closed to the atmosphere except through a ball check valve H2 which permits air to enter the tank to replace the fuel as it is used by the engine. To permit the withdrawal of fuel from the tank regardless of position, a flexible tube H4 having a relatively heavy end piece H6 to keep theend of the tube submerged in the fuel is connected to conduit 28 at the inlet thereof indicated at numeral H8, said end piece preferably being a metallic tubular member having a fuel strainer or filter inserted therein.

A pump, generally shown at numeral I4, is provided to deliver fuel at a substantially constant pressure from the tank to the centrifugal pump 32 and consists of fuel inlet and outlet check valves I20 and I22 respectively, a fuel chamber I24, a fuel impervious diaphragm I26, a calibrated spring I28 for urging said diaphragm in the fuel delivery direction and a linkage I30 between said diaphragm and a cam or the like (not shown) for actuating the pump. In the operation of the pump I4, downward movement of diaphragm I26 draws fuel from tank I through valve I20 into chamber I24 and upward movement thereof feeds the fuel through valve I22 and conduit 26 to the centrifugal pump under the pressure of spring I28. The diaphragm I26 gets its motion from an eccentric (not shown) through linkage I30 which provides for variable movement as required for the operation of the If a pump such as the one shown in the drawings is used, it may be desirable to include in conduit 26 a means, such as that shown at I40, to remove the pump pulsation. The means shown consists of a housing I42 having therein a fuel chamber I44, a diaphragm I46 and a spring I48 reacting between said diaphragm and one side of said housing. Any other suitable pump cap-able of supplying fuel to the impeller at a substantially constant pressure may be substituted for pump I4 and pulsation removing means I40. A positive displacement pump in combination with a pump by-pass has been found satisfactory.

In the operation of the present fuel metering system, liquid fuel is delivered by pump I4 from tank I6 to impeller 34 of the centrifugal pump 32. The fuel received by the impeller is discharged under increased pressure into conduit 46 from which it flows through variable metering orifice 42 into conduit 44 and chamber 46 urging diaphragm 54 away from the inlet of nozzle 26, permitting said fuel to discharge through the nozzle into the induction passage posterior to the throttle valve. The fuel delivered by impeller 34 also flows through conduit '12 into chamber I0 through orifice 68, passage 66 into chamber 50 between diaphragms 54 and I65. When throttle valve 22 is moved in the opening direction, the effective size of orifice 68 is decreased, causing a lowering of the pressure in chamber 50. As a result, diaphragm 54 moves further away from the inlet of discharge nozzle 26 and permits an increase in the discharge of fuel into the induction passage.

When the engine becomes inoperative and the impeller is no longer pumping fuel from passage 30 into conduit 40 and thence into chamber 46, the pressures of the fuel in chambers 46 and 50 readily become equal to one another so that diaphragm 54 floats between the two chambers. Thus, if no means were provided to prevent fuel from discharging into the induction passage, a small quantity of fuel would seep between the diaphragm and the inlet of discharge nozzle 26 and would in time flood the engine. To prevent this, the spring 96 is placed behind diaphragm I to urge said diaphragm against diaphragm 54 and thereby to seat the central portion of the latter diaphragm over the inlet of nozzle 26. Under certain engine operating conditions, the temperature may become so high that the absolute fuel pressures in the system and consequently in chambers 46 and 50 will increase to a 6 point where spring 96 alone could not seat said diaphragm over the inlet of discharge nozzle 26 when the engine is shut off. To offset the high pressure in chambers 46 and 50, the tank pressure is transmitted through conduits I08 and I06 to chamber 98, and through passage I I0 to the impeller and thence through the various passageways to chambers 46 and '50. Thus, when the engine is inoperative, the pressures in the three chambers are equalized so that the effective force of spring 66 remains unaffected by variations in the absolute pressures in the fuel system.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of parts may bemade to suit requirements.

We claim: I

1. In a fuel supply system for an engine having an induction passage with a throttle therein: a conduit having a discharge nozzle in said induction passage, 2. means for varying the pressure of the fuel in said conduit in accordance with engine speed, a fuel metering restriction in said conduit posterior to said pressure varying means, a passageway communicating with the conduit anterior and posterior to said pressure varying means to create a fuel control pressure, a member responsive to metered fuel pressure and to said control pressure for regulating the discharge of fuel through said nozzle, a resilient means for stopping the flow of fuel through said nozzle, and a second member responsive to said control pressure for rendering said resilient means ineffective while said engine is in operation.

2. In a fuelsupply system for an engine having an induction passage with a throttle therein, a conduit having a discharge nozzle in said induction passage, a means for varying the pressure of the fuel in said conduit in accordance with engine speed, a restriction in said conduit between said pressure varying means and said nozzle for metering the fuel delivered to said engine, a means for varying the effective size of said restriction, a passageway communicating with the conduit anterior and posterior to said pressure varying means to create a fuel control pressure, a member responsive to metered fuel pressure and to said control pressure for regulating the discharge of fuel through said nozzle, a resilient means for stopping the flow of fuelthrough said nozzle when the engine is inoperative, and a second member responsive to said control pressure for rendering said resilient means ineffective while the engine is in operation.

3. In a fuel supply system for an engine having an induction passage with a throttle therein, a conduit having a discharge nozzle in said induction passage, a means for varying the pressure of the fuel in said conduit in accordance with engine speed, an orifice in said conduit posterior to said pressure Varying means for metering the fuel delivered to said engine, a discharge valve adjacent said nozzle, a passageway communicating with the conduit anterior and posterior to said pressure varying means, a pair of spaced restrictions in said passageway for forming a fuel control pressure therebetween, a means regulated in accordance with throttle position for varying the effective size of one of said restrictions, a member responsive to metered fuel pres- I sure and to said control pressure for regulating said discharge valve, a resilient means for urging said valve to its closed position when the engine is inoperative, andfa second member responsive to said control pressure for rendering said resilient means ineiiective while said engine is in operation.

4. In a fuel supply system for an engine having an induction passage with a throttle therein, a conduit leading from a source of fuel and having a discharge nozzle in said induction passage, a means for varying the pressure of the fuel in said conduit in accordance with engine speed, a fuel metering restriction in said conduit posterior to said pressure varying means, a discharge valve adjacent said nozzle, a passageway communicating with the conduit anterior and posterior to said pressure varying means to create a fuel control pressure, a member responsive to metered fuel pressure and to said control pressure for regulating said discharge valve, a resilient means for urging said valve to its closed position, a second member responsive to said control pressure for rendering said resilient means ineffective while said engine is in operation, and a passageway communicating with said source for rendering said last mentioned membed also responsive to the pressure at said source.

5. In a fuel supply system for an engine having an induction passage with a throttle therein, a conduit leading from a source of fuel and having a discharge nozzle in said induction passage, means for varying the pressure of the fuel in said conduit in accordance with engine speed, a restriction in said conduit between said pressure varying means and said nozzle for metering the fuel delivered to said engine, a discharge valve adjacent said nozzle, a passageway communicating with the conduit anterior and posterior to said pressure varying means, a pair of spaced restrictions in said passageway forming a fuel control pressure therebetween, a member responsive to metered fuel pressure and to said control pressure for regulating said discharge valve, a resilient means for urging said valve to its closed position when the engine is inoperative, a second member responsive to said control pressure for rendering said resilient means ineffective while the engine is in operation, and a passageway communicating with said source for rendering said last mentioned member responsive to the pressure of the fuel at said source and also communicating with the inlet of said pressure varying means, whereby the fuel pressures on said members are equalized when the engine becomes inoperative.

G. In a fuel supply system for an engine having an induction passage with a throttle therein, a conduit connected to a fuel tank and having a discharge nozzle in said induction passage, a means for varying the pressure of fuel in said conduit in accordance with said engine speed, an orifice in said conduit between said pressure varying means and said nozzle for metering the fuel delivered to said engine, a means for varying the effective size of said orifice. a discharge valve adjacent said nozzle, a passageway communicating with the conduit anterior and posterior to said pressure varying means, a pair of spaced restrictions in said passageway for forming a fuel control pressure therebetween, a means regulated in accordance with throttle position for varying the effective size of one of said restrictions, a diaphragm responsive to metered fuel pressure and to said control pressure for regulating said discharge valve, a resilient means for urging said valve to its closed position when the engine is inoperative, a second diaphragm responsive to said control for rendering said resilient means ineffective while said engine is in operation, a passageway communicating with said tank for rendering said last mentioned diaphragm responsive to the pressure in said tank and also communicating with the inlet of said pressure varying means for returning fuel vapors to said tank, whereby the fuel pressures on said diaphragm are equalized when the engine becomes inoperative 7. In a fuel system, a main fuel supply passage, a fuel pressure control means in said passage, a valve in said passage posterior to said control means, a chamber for the fluid controlled by said valve, a second chamber for fluid controlling said valve, a pressure responsive member between said chambers adapted to actuate said valve, a third chamber disposed adjacent the second chamber and connected to said passage anterior to said control means, a second pressure responsive member between said second chamber and said third chamber, and a resilient element for urging said second pressure responsive member toward said first mentioned pressure responsive member to urge said valve to its closed position when the pressures in the three chambers are substantially equal.

8. In a fuel system, a main fuel supply pas sage, a fuel pressure creating means in said passage, a valve in said passage posterior to said pressure creating means, a chamber for the fluid controlled by said valve, a second chamber for fluid controlling said valve, 2. flexible diaphragm separating said chambers for actuating said valve, a third chamber disposed adjacent the second mentioned chamber and connected to said passage anterior to said fuel pressure creating means, a diaphragm separating said third chamber from said second chamber, and a resilient element in said third chamber for urging said second mentioned diaphragm toward said first mentioned diaphragm to urge said valve to its closed position when the pressures in the three chambers are substantially equal.

9. In a fuel supply system for an engine, a fuel control valve, a chamber for the fuel controlled by said valve, a second chamber for fuel for controlling said valve, a diaphragm separating said chambers for actuating said valve, 2. third chamber adjacent the second chamber for fuel at a pressure lower than that in the first two chambers, a diaphragm separating said third chamber from said second chamber, and a spring in said third chamber for urging said second mentioned diaphragm against said first mentioned diaphragm to urge said valve to its closed position when said engine is inoperative.

EMIL O. WIRTH. FREDERIK BARFOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,051,295 Gauger Aug. 18, 1936 2,272,815 Otto Feb. 10, 1942 2,374,844 Stokes May 1, 1945 2,419,171 Simpson et al Apr. 15, 1947 2,426,153 Mock Aug. 19, 1947 2,433,958 Rausenberger Jan. 6, 1948 2,438,662 Greenland Mar. 30, 1948 2,438,663 Greenland Mar. 30, 1948 2,440,241 Armstrong Apr. 27, 1948 2,440,567 Armstrong et a1 Apr. 27, 1948 

